validator will brick with django 1.7 migrations

[minddust]

raise ValueError("Cannot serialize: %r\nThere are some values Django cannot serialize into migration files.\nFor more, see https://docs.djangoproject.com/en/dev/topics/migrations/#migration-serializing" % value)
ValueError: Cannot serialize: <bound method DjangoChoicesMeta.validator of <class 'md.apps.notifications.models.NotificationType'>>
There are some values Django cannot serialize into migration files.
For more, see https://docs.djangoproject.com/en/dev/topics/migrations/#migration-serializing

[sergei-maertens]

Thanks for reporting, this will be fixed in #24 when all tests pass.